1. Field of the Invention
The present invention relates to gauge systems for indicating the level of liquid intake and, particularly, to electronic gauges of the type which can produce either an alarm signal or an indication of tank liquid level.
2. Description of the Prior Art
U.S. Pat. No. 5,124,686 discloses a magnetic tank level alarm system including an elongated rod coupled to a float which rises and falls with the liquid level. Magnets on the rod actuate switches to trigger alarms when certain liquid levels are reached. That type of system can be subject to false alarm signals if the liquid level rapidly changes or apparently rapidly changes, such as in response to turbulence in the liquid or the like. Also, while that prior system can provide a direct visual indication to a user of the liquid level, it does not provide any remotely detectable liquid level indication.
U.S. Pat. No. 5,245,874 discloses an optical liquid level gauge which utilizes a slotted or apertured elongated surface coupled to a float. Light directed through the slots is detected by a pair of optical detectors arranged in quadrature relationship to produce a pulsating output signal. The quadrature relationship of the detectors permits an indication of the direction in which the level is changing. However, this particular sensor is embodied in a total precipitation gauge and is arranged to indicate only the maximum liquid level reached. Furthermore, this prior art optical gauge is sensitive to ambient light, which can produce false readings.